NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

The graph to the left
shows seasonal mean temperature averaged across the contiguous
United States based on long-term data from the U.S. Historical
Climatology Network (USHCN). The 2002 value
is estimated from preliminary Climate Division data using the
first difference approach. December-February 2002 ranked as the fifth
warmest such period in the 1895 to present record. The
preliminary nationally averaged temperature was 36.3° F
(2.4° C) which was 3.3° F (1.8° C) above the long-term
mean. Although not monotonic, winter temperatures in the US have
increased approximately 1.5°F (0.8°C)/century since 1895.
The December-February temperature values
from 1895 through 2002 are available.

The historically warm
winter season is due largely to an extensive
area of much above normal temperatures, and the lack of very
cold temperatures, during two of these three months. During
February 2002 some colder than average state temperature ranks
did occur, though even in this month, the north-central
and northeast regions experienced above to much above normal
temperatures. As seen in the map to the right, record warm
winter temperature rankings occurred in ten
states throughout the northeast quadrant of the country
for the winter period. As can be seen by the winter 500mb
height and anomalies map, there were significant positive
anomalies over the northeast USA, corresponding to the unsually
warm surface temperatures. Alaska's
temperatures were also above normal for the third consecutive
winter and averaged 4.7°F (2.6°C) above the 1961-1990 mean
for December-February.

December-February
Precipitation

The December
2001-February 2002 mean precipitation was below normal for the
contiguous US, ranking as 14th
driest in the 1895-2002 record. However, as can be seen in the
map to left, there was considerable regional variability. While
many states received near normal precipitation, several states (New
Jersey, South Dakota and Maryland) experienced record dryness
during the winter. Below normal precipitation occurred along the
entire Atlantic seaboard continuing the long-term drought
conditions in many of those states. Much below
normal precipitation also occurred in North Dakota and
Nebraska, as well as Arizona. In contrast, above normal
precipitation amounts occurred in Washington and Arkansas for
December-February.

November-February
Temperatures

The graph to the left
shows the four-month seasonal mean temperature averaged across the
contiguous United States based on long-term data from the U.S.
Historical Climatology Network (USHCN). The 2002 value
is estimated from preliminary Climate Division data using the
first difference approach. November 2001-February 2002 ranked as the
second warmest such period in the 1895 to present
record. November 1999-February 2000 was the warmest
November-February period on record. The preliminary nationally
averaged temperature was 39.2°
F (4.0° C) which was 3.8° F (2.1° C) above the
long-term mean.

The anomalously warm
November 2001-February 2002 period, like that for the
meteorological winter, is due largely to an extensive
area of much above normal temperatures (top tenth percentile),
and the lack of very cold temperatures (lowest tenth percentile),
during each of these four months. As seen in the graph to the
right, two-thirds of the contiguous U.S. was unusually warm in
November 2001, followed by approximately a quarter of the country
unusually warm in December and about a fifth unusually warm in both
January and February.

Aside from the very
cold outbreak of November and December 2000, the last four years
have been dominated by unusually warm temperatutes (see graph below
left). The graph below right shows how this winter's unusual warmth
fits into the pattern of the last decade. While episodes of
unusually warm weather occurred during the 1990s, the frequency of
cold outbreaks was greater during the first half of the
decade.

Twelve states in the
northeastern and north central U.S. had the warmest
November-February on record in 2002. These states included Maine,
New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut,
New York, New Jersey, Michigan, Wisconsin, Minnesota, and Iowa. An
area of much above normal temperatures extended from Maine to South
Carolina, then westward to the central and northern Plains
states.

National
Temperatures - February

The graph to the left
shows monthly mean temperature averaged across the contiguous
United States based on long-term data from the U.S. Historical
Climatology Network (USHCN). The value is
estimated from preliminary Climate Division data using the first difference approach.
February 2002 ranked as the 30th warmest February in the 1895 to
present record. The preliminary nationally averaged temperature was
36.8° F (2.7° C) which was 2.3° F (1.3° C) above
the long-term mean. The February temperature values
from 1895 through 2002 are available.

It is interesting to
note that since 1995, only one year (2001) had February
temperatures that were not much above average.

The February
Mean 500mb Height and Anomalies chart shows no large negative
or postive anomalies over the contiguous United States. However,
significant negative anomalies were observed over the west coast of
Alaska. These height anomalies are associated with above average
precipitation for the month. For the winter
season, there are more substantial positive anomalies over the
northeastern quadrant of the country, associated with the unusual
winter warmth and dryness.

A more detailed analysis
including how statewide and regionwide temperatures compare to
other years is available.

Temperature Departures

The map to the right,
based on approximately 250 airport stations, shows departures from
the 1961-1990 normal temperatures for February 2002. The largest
negative temperature anomalies occurred in northern Utah and
southern Idaho, but significant cold anomalies (-1.8° F[-1°
C]) occurred throughout the south-central region. Much of the rest
of the contiguous states experienced unusually warm weather, with
the largest positive anomalies of 9° F (5° C) or greater
over the Dakotas eastward through the northeastern quarter of the
country. The bulk of Alaska also had large positive anomalies.

Greater than normal
day-to-day temperature variability is particularly noticeable in a
swath from New Mexico through Colorado, Wyoming and up into Montana
and Idaho. This is associated with the unusually cool departures of
monthly mean temperatures in this region as seen both in the map
above and in an animated map of daily
temperature anomalies.

National Precipitation

The graph to the left
is a time series depicting precipitation averaged across the
nation. Based upon preliminary precipitation data, February 2002
was the second driest February on record following
7 months of near-normal precipitation nationally. However,
considerable regional variability has occurred over the last 6
months.

New
Jersey, Delaware and Maryland
experienced their driest February on record. Much below normal
precipitation for February is also evident in the mid-Atlantic
states ranging westward into the Tennessee Valley, and northward
into southern New England. Other states which experienced much
below normal precipitation are the Dakotas, Nebraska, Arizona and
Utah. Dryness also extends throughout most the southern half of the
contiguous US.

Precipitation Anomalies

The map to the right,
based on approximately 250 airport stations, shows February 2002
total precipitation as a percent of the 1961-1990 station normals.
Above normal precipitation generally occurred in Michigan and
Wisconsin and far southeastern Florida, while the rest of the
country was generally dry. Especially dry were the mid-Atlantic
states, back into the Ohio/Tennessee valleys, as well as
Nebraska,South Dakota and southern California and Arizona. Eastern
Alaska was also dry but the west coast experienced anomalous
wetness for February.

National
Snow Cover

Snow cover duration
for February 2002, as observed by satellite, was well below the
long-term average across the eastern and north central U.S. and in
parts of the West (see map to right). Above-average snow cover
duration occurred in a band across the central Plains, and in other
parts of the West, especially the Pacific Northwest. An animated map of satellite-observed daily snow cover
extent shows the daily progression of snow across North America
during February.

Mountain snowpack
measurements in the western U.S., provided by the USDA Natural Resources Conservation
Service, indicate a pattern of above average snowpack in the
Pacific Northwest and below average snowpack over the rest of the
Far West. The snowpack was especially low in the central Rockies
and the mountains of the Southwest. Early March observations of the
water
content of the snow cover made by remote automated stations in
the western mountains reveal a similar pattern (NRCS).
End-of-February snowpack
was below average across much of Alaska, but above average in the
state's south central and southeastern coastal areas.

The February 2002 snow cover in the north central and
northeastern U.S. contrasts sharply with the February snow cover of
just last year. As seen in maps from the National Weather Service
North
Central River Forecast Center, an end-of-February snow depth
several feet deep extended from the western Great Lakes across the
Upper Mississippi Valley in 2001 (see map below left). This year, a
heavy snow cover existed only in the favored snow belt areas to the
lee of Lake Superior (see map below right).

A similar contrast between snow depth for February 28, 2001 and
February 28, 2002 is evident in the Northeast. As seen in maps from
the National Weather Service Northeast River
Forecast Center, a notable snow cover extended to the coast all
along southern New England last year, with several feet of snow
lying on the ground in northern New England (see map below left).
The snow cover was largely absent this year, with only the higher
elevations of the north having several feet of snow on the ground
(see map below right).

The same contrast can be shown in seasonal snowfall in the
Northeast. Unusually warm temperatures this winter have been
accompanied by dry conditions. The drought in precipitation is
reflected in less snowfall across much of the region this year (see
map below right), compared to a much snowier season last year (see
map below left). Less than 4 inches (10.2 cm) of snow fell in New
York's Central Park from December to February, 15 inches (38.1 cm)
less than normal, and snowfall in Boston, Massachusetts, was less
than half of the normal 32 inches (81.3 cm). The exception was the
favored snowbelt areas. The warmer than average surface water
temperatures and the lack of very cold air over the Great Lakes
extended the lake-effect snow season well into late winter. Heavy
snow fell in the snowbelt areas of the Northeast as cold Canadian
airmasses moved across the warmer than normal lakes. Marquette,
Michigan, received 164 inches (416.6 cm) during the winter
season and had their snowiest month on record in February. Buffalo,
New York received a record 82.1 inches (208.5 cm) of snowfall in
December.

The long-term average
snowfall for the season through the end of February can be seen in
the map to the right. This map was created from the snow data
available through December 2000 for 4748 stations. A comparison of
the 2002 snowfall map (above right) with this
climatology map shows the below-average 2002 snowfall for most
of the Northeast.